1. Field of the Invention
The present invention relates generally to valves for use in the fluid circuits of refrigeration and air-conditioning systems and, more particularly, to compressor valves and line service valves.
2. Discussion
Compressor valves and line service valves have been commonly used in refrigeration system fluid circuits to direct the flow of refrigerant through the circuit or retain the charge of liquid or gaseous refrigerant while isolating a portion of the circuit to facilitate the repair and/or replacement of system components or to perform general system maintenance. Examples of such valves are illustrated in prior art FIGS. 1 and 2. FIG. 1 shows a typical valve, such as one that is commonly made out of brass or steel which is used on compressors in the refrigeration and air-conditioning industry. The valve 100 includes a primary stem operator 102 that is disposed for linear movement within a valve body 104 by a threaded engagement, indicated at 106. Packing, generally indicated at 108, seals the valve 100 at the primary stem operator 102 while still allowing it to be rotatable in the valve body 104. At one end of the stem operator 102 is a globe-type plug or closure element 110 that is operable to completely block off a fluid passage 112. The primary stem operator 102 is linearly positionable between an opened position (as shown in FIG. 1) and a closed position (not shown) when rotated. In the opened position, the closure element 110 is backseated against the valve body 104 at location 114 and fluid is capable of flowing through the valve 100. In the closed position, the closure element 110 is advanced into fluid passage 112 and seated against valve body 104 at location 116. In this position, fluid flow through the valve 100 is prevented.
FIG. 2 depicts a cast iron compressor valve which is generally used with fluid line diameters greater than or equal to 21/8". Very similar to the other compressor valve described above, the cast iron valve 120 includes a primary stem operator 122 that is disposed for linear displacement within a valve body 124 by a threaded engagement 126. Located at one end of the primary stem operator 122 is a globe-type closure element 128 which is operable to block off a fluid passage 130 through the valve. In the opened position, the closure element 128 is backseated against the valve body 124 at location 132 and fluid is capable of flowing through the valve 120. In the closed position, the closure element 128 is advanced into fluid passage 130 and seated against valve body 124 at location 134. In this position, fluid flow through the valve 120 is prohibited. The closure element 128 in the cast iron compressor valve 120 typically includes a plastic seat 136.
As shown in FIGS. 1 and 2 and described above, globe-type compressor and line service valves commonly include a threaded, reciprocating primary stem operator which serves to linearly displace a closure element within the fluid passage of a valve body between an opened and a closed position. When the valve is in the opened position, as is illustrated in FIGS. 1 and 2, the closure element is still located in the valve's fluid passage and, therefore, in the fluid flow stream. Because of this inherent design feature, blockage or interference within the fluid passage is created and, the fluid flow through the valve becomes turbulent, resulting in an increased pressure drop across the valve. The pressure drop, in turn, reduces the efficiency of the valve by allowing a significant amount of energy to be lost from the refrigeration circuit. Consequently, this energy loss presents a design constraint that must be addressed by refrigeration and air-conditioning system designers and engineers as they develop refrigeration and air-conditioning systems. Often, to compensate for the energy loss, system designers and engineers specify larger, over-sized compressors which exceed the thermodynamic requirements of the refrigeration system application. The use of such oversized compressors is inefficient and a waste of energy.
In the past, the refrigeration and air-conditioning industry has tolerated the occurrence of flow turbulence, pressure drop and the resulting energy loss which has been observed across refrigeration valves of the compressor and line service type. However, due to the increasing awareness of energy conservation and the attendant need to design and develop more energy efficient refrigeration and air-conditioning systems, it has become desirable to improve upon the efficiency of these types of refrigeration valves by reducing or eliminating the flow turbulence, pressure drop and associated energy loss experienced with them. In a typical application, for example, a series of compressors may be utilized in a refrigeration system such as the refrigeration section of a grocery store or supermarket, or the air-conditioning system of a large building. Improving the efficiency of compressor valves may enable fewer compressors to be used in a given application or allow a given number of compressors to work for shorter periods of time, or less than peak output thus saving not only significant amounts of operating costs in the form of electrical energy, but also significant equipment acquisition, repair and maintenance costs as well.
Further, it has been considered equally desirable that any improved efficiency valve maintain the ability to achieve a positive shut-off or seal as found in prior art globe-type valves wherein the application of a torque is translated into linear displacement. Presently, refrigeration valves having enhanced flow characteristics do not offer the feature of enhanced sealability.
It is, therefore, an object of the present invention to provide a valve for use in the fluid circuit of a refrigeration or air-conditioning system, such as a compressor or line service, that is significantly more energy efficient than present refrigeration valves by minimizing or substantially eliminating turbulence in the fluid flow path through the valve and the resulting pressure drop and energy loss. It is an additional object of the present invention to provide such an improved efficiency valve that also effectuates a positive seal.